The present invention relates to apparatus for the production of small clear ice bodies and comprises an evaporator connected to a refrigeration cycle with freezer cells open at the bottom or lower side, a water trough arranged below the evaporator and a mechanical spraying device for spraying water from the trough into the freezer cells.
U.S. Pat. No. 4,602,489 discloses a device containing a maximum number of freezer cells per evaporator area, since they are located side by side without interspaces between them. Due to the close arrangement of the freezer cells, a layer of ice forms not only in the freezer cells, but also on the bottom of the cells, whereby at the end of the cycle, all of the small ice bodies freeze together and form a single layer. Accordingly, a heatable grid or screen is located beneath the freezer cells and spaced from them. The grid cuts up the ice layer when the small ice bodies are collected. This technology has been disclosed previously in U.S. Pat. No. 2,747,375.
The water required to form the small clear ice bodies is sprayed into the center of each freezer cell by a respective water nozzle. The nozzles are secured in water tubes located below the freezer cells. The sprayed water does not freeze immediately, however, it has lost heat and runs down the cell walls onto the metal grid and freezes to the metal grid along with the small ice bodies which form in the downward direction. Any water not frozen to the grid returns to the pumping cycle.
As the small ice bodies grow in size, a continuous layer of ice develops. After a given time, the plastic insulation plate also reaches freezing temperature. As a result, a continuous layer or plate of ice is formed with the small ice bodies frozen to it.
During the defrosting operation, the freezer cells and the metal screen are heated. Thus, initially, the ice plate is detached from the metal screen and the small ice bodies are loosened from the metallic cell walls. Because of the poor thermal conductivity of the plastic plate, the small ice bodies cling to it for a longer time. Only after the plastic plate has heated up, is it possible for the small ice bodies to slide downwardly. During this time period, the small ice bodies in the freezer cells become progressively warmer and are considerably melted down, thus, an ice plate, with partially melted ice bodies frozen to it, falls onto the water tubes and only after the ice plate has melted, can the individual ice bodies fall onto an inclined diverting surface and pass into a storage container. In this procedure, the screen is cooled so that ice forms on it. Moreover, the nozzles tend, as is known, to become blocked by impurities and minerals contained in the water.
One disadvantage of this apparatus is the extended time required for the ice layer to melt, whereby a considerable amount of melt-water is produced, and a considerable amount of energy is required, first, to produce the ice layer, and then to melt through the layer.
It is also disadvantageous that the small ice bodies frozen to the plate must melt while supported on the water tubes before the individual small ice bodies can drop into the storage container. No ice production is possible during this time.
U.S. Pat. Nos. 3,043,117, 2,729,070, 2,722,110, 3,254,501, 3,386,258, 2,978,882 and 3,040,545; Great Britain Pat. No. 2,013,857, and French Pat. No. 1,571,033 disclose apparatus for the production of the small clear ice bodies where the freezer cells are spaced with respect to one another and the space therebetween is covered or filled with thermal insulating material. This insulating material should prevent formation of an ice layer which freezes all of the small ice bodies to one another.
The device in Great Britain patent application 2,013,857 and U.S. Pat. Nos. 3,254,501, 4,505,130 and 4,006,605 and French Pat. No. 1,571,033 demonstrate that the same could not be achieved in the manner described. In these known devices, the insulating material between the freezer cells is heated during defrosting of the small ice bodies and, indeed, in Great Britain patent application, 2,013,857 and U.S. Pat. Nos. 4,505,130 and 4,006,605, is heated by warm water, while in French Pat. No. 1,571,003, the heat is provided by a hot gas, and in U.S. Pat. No. 3,254,501, the heat is supplied by electric current. Experience has shown that none of these devices wa successful; neither is the formation of ice prevented, nor is the ice defrosted at the proper time.
As already indicated, the nozzles which spray the water into the freezer cells, tend to become clogged. Therefore, attempts have been made to spray the water into the freezer cells using simple mechanical devices. In this regard, U.S. Pat. No. 3,386,258 proposes a multiple-blade propeller which revolves about a vertical axis with the blades dipping slightly into the trough water and producing a water mist. The efficiency of this device is very low. In addition, the water level in the trough must be controlled accurately.
U.S. Pat. No. 2,729,070 proposes the use of discs rotating around a horizontal shaft and plunging into the water trough. Such discs convey only a small amount of water which clings to them by adhesion. Moreover, the spraying direction cannot be controlled, whereby only a small amount of water reaches the freezer cells.
To improve the conveying efficiency, U.S. Pat. No. 2,722,100 proposes arranging vanes on the sides of the rotating discs. In such an arrangement, however, the water clings to the vanes also due to adhesion, so that again very little water is conveyed and is sprayed mainly in the wrong direction. Furthermore, control of the water level in the trough in also required in this arrangement.
During a freezing cycle pollutants and minerals become centratrated in the residual water in the trough. For this reason, the trough is emptied prior to being refilled with fresh water. In order to empty the trough, either it is tilted, or an electromagnetic valve in the discharge pipe is opened. In the latter instance, there is the danger that the function of the valve is obstructed by particles of dirt or minerals.
If it is attempted to increase the ice-producing capacity of known apparatus, for instance, to 1,000 kg or more of the small ice bodies per day, by appropriately increasing the dimensions of the evaporator, trough, spraying device, and the like, then they become bulky and uneconomical. The actuators for swivelling the trough and for pumping the water become large and heavy, the dead volumes increase the size of the housings, the electrical terminal load reaches values which can no longer be provided, and other problems develop. For these reasons, the known apparatuses and also those constructed according to U.S. Pat. No 3,654,771 are available commercially with only relatively small capacities of, for example, a maximum of 250 kg per day.